cnn's casey wian is at nasa's jet propulsion lab in pasadena, california. casey? >> reporter: here at jpl, they've been tracking that asteroid for a year. and just about 3 1/2 hours ago, it came oh, so close to planet earth. it may not look like much, a tiny blip speeding across the screen, but asteroid 2012da14 packs a powerful punch. fortunately, the punch missed. scientists say an asteroid with a similar 150-foot diameter collided with earth 50,000 years ago in arizona creating this crater and obliterating everything in a 50-mile radius. >> this is a rare opportunity to see a small asteroid up close. it's very rare. an asteroid of this size doesn't come close to the earth more than once every 40 years on average. >> reporter: the asteroid raced past and missing earth by 17,000 miles. it came close to threatening satellites close to the earth. nasa is using radar and other technology to study how the asteroid behaves, including its rotation rate, its composition and how it's impacted by the earth's gravity. the idea is to learn enough to prevent catastrophe from